A few days ago, the Reddit reaction to the announcement of Dropbox's general availability resurfaced:
For a Linux user, you can already build such a system yourself quite trivially by getting an FTP account, mounting it locally with curlftpfs, and then using SVN or CVS on the mounted filesystem. From Windows or Mac, this FTP account could be accessed through built-in software
My response? Well, it turns out I posted that back in 2011: https://sysadmin1138.net/mt/blog/2011/08/your-very-own-dropbox-that-isnt-dropbox.shtml
Novell iFolder. It totally was file-sync-and-share (FSS) like Dropbox, but you hosted it yourself. Here is a Wayback Machine link to the iFolder product page circa 2011. Not only that, I first blogged about iFolder way back in 2005. I was very skeptical about Dropbox when it first came out, simply because I'd been using a technology just like that for years already.
However...
What I failed to grasp was that Dropbox was cloud-based, networks were now fast enough for an Internet-based FSS solution, and Dropbox would work on mobile w-a-y faster than Novell ever managed. In short, first-mover is not always best-mover.
Today, the FSS space is crowded and the corporate managed file-servers I spent 14 years of my career maintaining are antiquated relics mostly found in large universities and older enterprises. These days if your word processor or spreadsheet maker isn't putting files directly into the cloud (Office 365, Google Apps, etc), you're putting the files into a directory that is synced to the cloud using an FSS solution.